1. Field
One embodiment of the invention relates to a storage device, a head position detection method, and a control circuit for detecting a head position from a head read signal.
2. Description of the Related Art
Phase demodulation and area demodulation have been known as demodulation to detect the head position from a servo pattern recorded on a magnetic disc medium.
In the phase demodulation, a predetermined phase servo pattern is recorded on a magnetic disc medium and a phase angle indicating the head position is demodulated from a head read signal. The head position obtained as a result of the demodulation is linear since a track boundary does not exist, in principle, in phase demodulation.
On the other hand, in the area demodulation, an area demodulation pattern known as a two-phase servo pattern is recorded on a magnetic disc medium. Then, two types of demodulation signals, which differ in phase by 90°, are generated by addition and subtraction of a head read signal, and the head position is detected by switching the demodulation signal at the track boundary. Reference may be had to, for example, Japanese Patent Application Publication (KOKAI) No. 2000-215627 and Japanese Patent Application Publication (KOKAI) No. 7-287949.
In such conventional area demodulation, however, it is difficult to smoothly connect two types of demodulation signals at the track boundary due to difference in gain, etc. of the demodulation signals, and a position signal may be discontinuous.